1. Field of the Invention
The present invention relates to a positioning device for a sensor element of a miniature fan, and more particularly to a positioning device for positioning a sensor element of a miniature fan to minimize thickness of the miniature fan and to locate the sensor element in an optimal position for detection.
2. Description of the Related Art
It is known to use a sensor element for detecting polarity of the rotor of a miniature fan, thereby sending signals to change polarity of the stator winding for providing alternating magnetic fields. The miniature fan may retain the best operational quality if the sensor element can be located in the optimal position relative to the stator magnetic poles.
U.S. Pat. No. 5,967,763 issued to Horng on Oct. 19, 1999 disclose optimal positioning devices for a sensor element of a miniature fan, wherein the sensor element mounted on a circuit board is located on a vertical line extending from one of the first end edge and the second end edge of one of the poles of the coil seat. Miniaturization is a trend in miniature fans. The above-mentioned positioning devices may provide required positioning effect for the sensor element for providing improved operational effect, but the overall thickness of the resultant miniature fan cannot be further reduced. In addition, if the thickness of the miniature fan is further reduced, the positioning uniformity for the sensor element relative to front end edge or rear end edge of magnetic poles of the stator becomes relatively difficult.
It is an object of the present invention to provide a positioning device for a sensor element of a miniature fan in which the sensor element can be easily and conveniently engaged and fixed in an optimal detecting position relative to the stator poles, thereby providing improved operational effect for the miniature fan. The quality of the produced miniature fans is more consistent.
It is a second object of the present invention to provide a positioning device for a sensor element of a miniature fan, wherein the overall thickness of the miniature fan is relatively small after engagement of the sensor element, thereby providing a super thin miniature fan for market needs.
A positioning device in accordance with the present invention includes an axle tube for engaging with a circuit board and a stator. The circuit board includes control elements and a sensor element thereon. Each pole of the stator includes two pole ends. A gap exists between two adjacent pole ends respectively of two adjacent poles. The gap receives the sensor element or provides a positioning reference for the sensor element.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.